Colour printers are becoming evermore common while requirements on the user-friendliness of the printers increases. The paper that is used in colour printers is glossy or slippery when print has been applied, with very low friction between sheets. Furthermore, the paper used is sensitive to mechanical treatment, and blemishes readily arise in the paper. This leads to problems in roller stages in booklet makers that are currently known. The low friction between the sheets often results in these being separated from each other when the stapled stack of sheets enters between the rollers, that is, the outermost sheet is torn from the booklet. It is currently attempted to solve this problem for this type of machine by manually adjusting with a lever a suitable separation of the rollers of the second pair of rollers. This adjustment must be carried out individually for each booklet thickness and booklet size and the result is often that the booklet after the roller stage has an increased projected booklet height, see FIG. 1, where the projected booklet height a for a schematically shown booklet 2 is illustrated.
Booklet makers are also previously known with motorised, computer-controlled servosystems for adjusting the separation of the rollers of the second pair of rollers as specified by input data. This servosystem is very complex and expensive and thus can only be used on large printing machines.